Harrell emerged in Houston with a big 2012 campaign. He racked up 193 2/3 frames of 3.76 ERA ball that year, striking out 6.5 and walking 3.6 batters per nine while emerging as a popular trade target. But Houston thought it had a durable, solid starter with plenty of control, and did not deal him until it was too late to bring much value.

Harrell took a steep downturn in 2013, throwing to a 5.86 ERA in his 153 2/3 innings while both striking out and walking 5.2 per nine. After a rough start to the year last season, Harrell was shipped to the D’backs for a PTBNL and ultimately ended up with another rather ugly line at Triple-A for Arizona.